An ion implanting technology holds an important position in a semiconductor fabricating process or the like in recent times.
In implanting ions to a target, for example, a semiconductor substrate, it is known that an implantation characteristic particular in an implantation depth direction is indicated by an implantation angle (incidence angle) relative to a crystal axis of the semiconductor substrate and it is normally requested for the ion implanting technology to enable to execute an ion implanting processing under a condition of preventing the implantation characteristic or positively utilizing the implantation characteristic.
The above-described phenomenon referred to as channeling is provided with a high incidence angle dependency particularly at a vicinity of 0 degree of the incidence angle of ions and therefore, although an incidence angle control with higher accuracy is requested at a vicinity of 0 degree of the incidence angle, the incidence angle control with high accuracy is normally requested at other incidence angle.
Japanese Patent Gazette No. 3358336 (paragraphs 0002, 0003, FIG. 1) (hereinafter, Patent Reference 1) describes an example of an ion implanting apparatus capable of meeting such a request to some degree. FIG. 1 shows an ion implanting apparatus similar to the ion implanting apparatus described in Patent Reference 1.
The ion implanting apparatus is provided with an ion source 2 for generating an ion beam 4, a mass separator 6 on which the ion beam from the ion source 2 is incident and which separates to sample a desired mass of the ion beam 4 from the ion beam 4, an accelerator/decelerator 8 on which the ion beam from the mass separator 6 is incident and which accelerates or decelerates the ion beam 4, an energy separator 10 on which the ion beam 4 from the accelerator/decelerator 8 is incident and which separates to sample a desired energy of the ion beam 4, a scanner 12 on which the ion beam 4 from the energy separator 10 is incident and which scans the ion beam 4 in x direction (for example, horizontal direction), a beam parallelizer 14 on which the ion beam 4 from the scanner 12 is incident and which bends back the ion beam 4 to parallelize to be in parallel with z axis, mentioned later, and a target driving apparatus 20 (refer also to FIG. 7) for mechanically reciprocating to scan (reciprocating to drive) a target (for example, a semiconductor substrate) 16 in y direction (for example, vertical direction) orthogonal to the x direction or mechanically reciprocating to scan (reciprocating to drive) the target substantially in y direction in a region of irradiating the ion beam 4 from the beam parallelizer 14.
Here, the z axis is defined in a direction orthogonal to the x direction (in other words, x axis) and the y direction (in other words, y axis) and in a direction of a trajectory of the ion beam 4 incident on the target 16 in view of design.
The mass separator 6 is, for example, a mass separating electromagnet for separating the mass of the ion beam 4 by a magnetic field. The accelerator/decelerator 8 is, for example, an accelerator/decelerator tube having a plurality of sheets of electrodes for accelerating or decelerating the ion beam 4 by a static electric field. The energy separator 10 is, for example, an energy separating electromagnet for separating the energy of the ion beam 4 by a magnetic field. The scanner 12 is, for example, a scanning electromagnet for scanning the ion beam 4 by a magnetic field or a scanning electrode for scanning the ion beam 4 by an electric field. The beam parallelizer 14 is, for example, a beam parallelizing electromagnet for parallelizing the ion beam 4. For example, also in reference to FIG. 7, the target driving apparatus 20 includes a holder 18 for holding the target 16 and reciprocates to scan the target 16 held by the holder 18 in the y direction or substantially in the y direction as shown by an arrow mark 22.
By the above-described constitution, ion implantation can be carried out uniformly by irradiating the ion beam 4 having the desired mass and the desired energy to the target 16 while scanning the ion beam 4 parallelly in x direction, mechanically reciprocating to scan the target 16 held at a predetermined angle relative to the ion beam 4 in y direction and uniformly irradiating the ion beam 4 to an entire face of the target 16. The type of using both of electromagnetic scanning of the ion beam 4 and mechanical scanning of the target 16 in this way is referred to as hybrid scanning type.
In this case, ideally, inspecting apparatus on a beam line of the ion beam 4, for example, the mass separator 6, the energy separator 10, the scanner 12 and the beam parallelizer 14 are designed to deflect the ion beam one-dimensionally only in x direction and not to deflect the ion beam 4 in y direction. Therefore, a surface of the target is irradiated with the ion beam 4 by a constant incidence angle by accurately controlling a parallelism of the ion beam 4 in x direction.
Here, the incidence angle of the ion beam 4 relative to the target 16 is a relative angle between the target 16 and the ion beam 4, specifically, refers to an angle made by a perpendicular line erected on the surface of the target 16 and the ion beam 4. Explaining further in details, in the incidence angle, there are an incidence angle φx in x direction as in an example shown in FIG. 10A (that is, in x-z plane) and an incidence angle φy in y direction as in an example shown in FIG. 10B (that is, in y-z plane). Numeral 17 designates the perpendicular line. For example, the target 16 shown in FIG. 7 is an example of a case in which the incidence angle φy in y direction is held to be larger than 0 degree similar to the example of FIG. 10B.
As in an example shown in FIG. 2, a parallelism of the ion beam 4 in x direction refers to an angle θx made by a trajectory actually tracked in x-z plane by the scanned and parallelized ion beam 4 and the z axis direction. Therefore, θx=0° in an ideal case in which the scanned and parallelized ion beam 4 tracks a trajectory completely in parallel with z axis. Further, the parallelism θx in the x direction and the incidence angle φx in the x direction are much related to each other.
Further, as in an example shown in FIG. 3, an angle made by a trajectory actually tracked in y-z plane by the scanned and parallelized ion beam 4 and z axis direction is designated by notation θy and is referred to as an angle deviation in y direction of the ion beam 4 in the specification. Therefore, for example, in an ideal case in which the scanned and parallelized ion beam 4 tracks a trajectory completely in parallel with z axis, θy=0°. Further, the angle deviation θy in the y direction and the incidence angle φy in the y direction are much related to each other.
Generally, as amounts of characterizing a charged particle beam, or the ion beam 4 in this case, other than a total beam current, there are (a) a center trajectory tracked by a center of the ion beam 4 having a beam current density distribution, (b) a beam size showing spread of the beam current density distribution in a face perpendicular to the center trajectory, (c) a diverging angle representing a shift in a direction of moving respective constituent ions relative to a direction of the center trajectory of the ion beam 4 and the like. A further specific definition thereof will be mentioned later in reference to FIG. 4 through FIG. 6.
When ion implantation is carried by irradiating the ion beam 4 to the target 16, the most important element as the incidence angle of the ion beam 4 is the incidence angle of the center trajectory of the above-described (a) to the target 16. By setting the incidence angle to a desired value, a large portion of ions constituting the ion beam 4 are incident on the target 16 by a desired incidence angle as an average. However, actually, respective ions constituting the ion beam 4 are respectively provided with diverging angles and therefore, incidence angles of respective ions are present with some width at a surrounding of the incidence angle of the center trajectory.
Therefore, when the control of the incidence angle of the ion beam 4 with higher accuracy is requested, it can be said that first, it is important to enable to control the incidence angle of the center trajectory of the ion beam 4 with high accuracy and successively, it is preferable to enable to control the diverging angle with high accuracy.
A technology capable of partially meeting such a request, Japanese Patent Gazette No. 2969788 (sixth paragraph-eleventh paragraph, FIG. 1 through FIG. 9) (hereinafter, Patent Reference 2) describes a technology in which a forestage multipoints Faraday and a poststage multipoints Faraday constituted by respectively aligning pluralities of detectors for measuring a beam current of the ion beam in a direction of scanning the ion beam (for example, the x direction) are respectively provided on an upstream side and a downstream side of a target, in the two multipoints Faradays, at which position in the beam scanning direction the scanning ion beam is disposed at the same time is measured and from a result thereof, a parallelism in the beam scanning direction of the ion beam in a space between the multipoints Faradays (that is, the parallelism θx in the x direction) is measured.
A forestage multipoints Faraday 24 illustrated in FIG. 7 corresponds to the above-described forestage multipoints Faraday and a poststage multipoints Faraday 28 corresponds to the above-described poststage multipoints Faraday. The two multipoints Faradays 24, 28 are respectively provided with the pluralities of detectors (for example, Faraday Cup, not illustrated). In an example of FIG. 7, front sides of the respective detectors are respectively provided with inlets, 26, 30 in a slit-like shape.
The parallelism θx in x direction of the ion beam 4 can be measured by using the forestage multipoints Faraday 24 and the poststage multipoints Faraday 28 in accordance with the technology described in Patent Reference 2. Further, the parallelism θx in x direction of the ion beam 4 can also be controlled with high accuracy by controlling a drive current or a drive voltage of the beam parallelizer 14 in accordance with the technology described in Patent Reference 2 based on the measurement information. Thereby, the incidence angle φx in x direction of the ion beam 4 can accurately be controlled by accurately aligning the center trajectory of the ion beam 4 in x-z plane in z axis direction.
For example, with higher function formation, finer formation or the like of a semiconductor device, the ion implanting technology tends to be requested to enable to control the incidence angle with higher accuracy such that when a further specific example is printed out, ion implantation having a steep implantation boundary can be realized. For that purpose, it is important to also accurately control the incidence angle of the ion beam 4 in y direction orthogonal to the direction of scanning the ion beam (x direction) which has not been problematic in the background art.
Particularly, with miniaturization of a semiconductor fabricating process, it becomes more and more important in the future to transport the ion beam 4 having low energy to irradiate to the target 16 in order to shallow an ion implanting depth, however, when the energy of the ion beam 4 becomes low, the ion beam 4 tends to be strongly provided with the diverging angle by electric repulsion of ions constituting the ion beam 4 (which is referred to as a space charge effect).
Therefore, in order to control the incidence angle with high accuracy, first, it is important to measure and monitor one, preferably both of the angle deviation θy in y direction orthogonal to the direction of scanning the ion beam 4 and the diverging angle.
Further, for example, the above-described case of the ion implanting apparatus of the hybrid scan type, although normally, a speed of scanning the target 16 in y direction is lower than that in scanning the ion beam 4 in x direction, when the scanning speed in y direction is accelerated in order to promote productivity, there is a high possibility that uniformity of implantation to the target 16 is influenced by a width of distributing the ion beam 4 in y direction (beam size). Particularly, when the beam size in y direction of the ion beam 4 becomes extremely small, the uniformity of implantation is deteriorated and therefore, in order to ensure high implantation uniformity, it is also preferable to measure the beam size in y direction of the ion beam 4 and monitor the beam size on the target 16.
However, when a Faraday measuring system quite separately from the forestage multipoints Faraday and the poststage multipoints Faraday which have been provided in the background art for measuring the parallelism in x direction of the ion beam 4 or the like is newly provided in order to measure the angle deviation θy in y direction, the diverging angle, and the beam size of the ion beam 4, (a) the measuring system is increased, the structure becomes complicated and also cost is considerably increased, (b) in measuring operation, an operation of interchanging the measuring system in x direction and the measuring system in y direction is obliged to be carried out with respect to the beam line of the ion beam 4, a time period required for the interchanging operation becomes an extra time period and the productivity is lowered.